Impregnated-type cathode substrate with large particle diameter low porosity region and small particle diameter high porosity region

Abstract

There is provided an impregnated-type cathode substrate comprising a large particle diameter low porosity region and a small particle diameter high porosity region which is provided in a side of an electron emission surface of the large particle diameter low porosity region and has an average particle diameter smaller than an average particle diameter of the large particle diameter low pore region and a porosity higher than a porosity of the large particle diameter low porosity region, the impregnated-type cathode being impregnated with an electron emission substance.

What is claimed is:  
     
       1. A method of manufacturing an impregnated-type cathode substrate comprising: 
       forming a porous sintered body to produce a large particle diameter low porosity region;  
       producing a porous cathode pellet by forming a small particle diameter high porosity region in an electron emission surface side of the porous sintered body, said small particle diameter high porosity region having an average particle diameter smaller than that of the large particle diameter low porosity region and a porosity higher than the porosity of the large particle diameter low porosity region;  
       cutting or punching the porous member, forming a porous cathode substrate thereby; and  
       impregnating the porous cathode substrate with an electron emission substance.  
     
     
       2. A method according to  claim 1 , wherein the small particle diameter high porosity region is formed by a method selected among a printing method, a spin-coating method, a spraying method, an electrocoating method, and an elution method. 
     
     
       3. A method of manufacturing an impregnated-type cathode substrate comprising: 
       forming a porous sintered body to produce a large particle diameter low porosity region;  
       producing a porous cathode pellet by forming an small particle diameter high porosity region in an electron emission surface side of the porous sintered body, said small particle diameter high porosity region having an average particle diameter smaller than that of the large particle diameter low porosity region and a porosity higher than that of the large particle diameter low porosity region;  
       providing a filler selected from a group consisting of metal and synthetic resin having a melting point of 1200° C. or less, in an electron emission surface side of the porous cathode pellet;  
       heating the porous cathode pellet provided with the filler, at a melting temperature of the filler;  
       cutting or punching the porous sintered body into a predetermined size, forming a porous cathode substrate thereby;  
       subjecting the porous cathode substrate to tumbling processing, removing burrs and contaminations thereby;  
       removing the filler from the porous cathode substrate subjected to the tumbling processing; and  
       impregnating the porous cathode substrate having the removed filler, with an electron emission substance.  
     
     
       4. A method of manufacturing an impregnated-type cathode substrate comprising; 
       forming a sintered body made of high melting point metal to form a large particle diameter low porosity region;  
       preparing paste containing high melting point metal powder having an average particle diameter smaller than that of the large particle diameter low porosity region and at least one kind of filler selected from a group of metal and synthetic resin having a melting point of 1200° C. or less;  
       applying the paste to an electron emission surface side of the porous sintered body made of high melting point metal to form the large particle diameter low porosity region;  
       heating the porous sintered body made of high melting point metal of the large particle diameter low porosity region applied with the paste, to a temperature at which the filler can be melted, such that a small particle diameter high porosity region having an average particle diameter smaller than that of the large particle diameter low porosity region and a porosity higher than that of the large particle diameter low porosity region is formed, thereby to obtain a porous cathode pellet;  
       cutting or punching the porous sintered body into a predetermined size, forming a porous cathode substrate thereby;  
       subjecting the porous cathode substrate to tumbling processing, removing burrs and contaminations thereby;  
       removing the filler from the porous cathode substrate subjected to the tumbling processing; and  
       impregnating the porous cathode substrate with an electron emission substance.